The authors explore the inner workings of coalition government inside No 10, the Cabinet Office, Whitehall departments and Parliament. “Thanks to support from David Cameron and Nick Clegg, we got to see how the coalition works from the inside” Professor Hazell said. “Watching them in action quickly exploded the British myth that coalition government must be unstable, weak, and indecisive. This one was remarkably bold and decisive – and at the centre, remarkably harmonious”.

But it was a different story in Parliament. “As one of our interviewees said, ‘What we have is a coalition government, not a coalition Parliament’” Dr Yong added. “Parliament has seen unprecedented rebellions from the government’s supporters, from both parties. The government has survived so far thanks to its majority. But the troops are not happy, and if the coalition collapses, it will be in Parliament that it happens”.

In some 150 interviews conducted as research in action, candour was shown to us by ministers, parliamentarians, special advisers, officials of both parties, senior civil servants and media commentators. The book is full of quotations about the highs and lows, and the do’s and don’ts of coalition government.

Key observations and lessons in the book

We conclude: “The Coalition in its first eighteen months set a model for harmonious and unified government which may prove hard to follow.” We were told again and again that it was proving to be a more united government than its single party predecessor under Gordon Brown. But in year 3 its unity and stability will really be tested, with mounting tensions over the deficit reduction strategy and Europe.

The parties thought hard about a comprehensive mid term review, but decided against. At this stage, it would only accentuate divisions.

The government could bring in fresh faces in a reshuffle, and draw on the larger talent pool of the Lib Dems in the Lords.

The Conservatives must take care under pressure to stay generous to the Lib Dems.

The government could still survive if the Lib Dems were to quit, by substituting a minority government depending on a confidence and supply agreement.

An electoral pact could bring gains for the Lib Dems in the short term, but prove to be a double edged sword in the long term.

Lessons for future Parliaments in case they’re hung

All parties need to write their manifestos with coalition in mind, as well as single party government.

To keep open the possibility of coalition, parties need to maintain working relations with each other up to the election. Labour got this wrong in 2010.

If there is another hung parliament more time should be allowed for interparty negotiations.

The parties could also allow more input from the civil service to the negotiations.

Before the debate on the Queen’s Speech the Commons should hold a vote of confidence in the new Prime Minister (an investiture vote). That would confirm the outcome of the negotiations, and enable the Commons to approve any coalition agreement.

Lessons for the major coalition partner

Maintain a golden rule of good faith and no surprises

Ensure that the party leadership has an efficient mechanism for consulting the wider party. The Conservatives were lacking this in 2010.

Remember that coalition limits the opportunities for advancement, and strains the loyalty of backbenchers. Reward them in other ways.

Ensure that minority party staffers are integrated into the No 10 operation

Lessons for the minor coalition partner

Try to choose cabinet posts which will score with the voters. Think hard about whether to go for breadth or depth of influence.

More special advisers and other support are needed: include this in the coalition agreement.

Lessons for the parties in Parliament

Develop effective backbench committees with good access to senior ministers

Involve those committees in developing future policy

Media handling

Hopes that spin was dead because of the need to check out policy with two centres of power were not fulfilled. The unity/distinctiveness dilemma which is inherent in all coalition governments was often played out in the full glare of publicity or in lobby stories. Overarching coalition messages tended to get lost.

Some of this “differentiation” but by no means all of it, was choreographed between the PM and DPM. Andy Coulson the first No 10 director of communications ‘had an instinct not a strategy’ for coalition publicity management. His departure coincided with an overdue strengthening of the centre of government. But media management became overshadowed by phone hacking, Murdoch and what became the Leveson agenda.